Ballast water treatment monitoring system

ABSTRACT

A method and system for taking a sample of ballast water. The method includes withdrawing a sample of ballast water via a tube inserted in a ballast water pipe, wherein the tube includes a sample inlet, and isokinetic flow is achieved via a pump that controls the flow of the sample ballast water through the tube inlet by comparing a flow of the ballast water pipe with a flow of the sample ballast water through the tube; and controlling the flow of water through the sample tube inlet when a flow of the ballast water pipe is sensed to be different; withdrawing a portion of the sample ballast water for testing; and returning remaining sample ballast water to the ballast water pipe.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.61/646,682, filed on May 14, 2012, incorporated herein by reference inits entirety.

BACKGROUND

Many regulations exist for the treatment and discharge of ballast waterby marine vessels. Ship ballast water treatment systems are typicallytested by an independent laboratory. These laboratories, even whenfollowing mandated test protocols, are not able to replicate all of thevariability in organism populations, water chemistry, and environmentalconditions that a marine vessel will encounter during operations. Thisleads to uncertainty that ballast water treatment systems will beeffective in varied conditions. Marine vessel operators and regulatoryagencies need tools and methods for reliable sampling of ballast waterto allow these determinations to be made.

SUMMARY

One of the primary concerns when sampling ballast water to determinecompliance with standards is the ability to obtain a representativesample. A sample is representative if it is gathered in a way tominimize any bias from the bulk fluid and is large enough to providestatistical significance from the results.

Minimizing bias in the sample is primarily a function of the samplingmethod and geometry of sampling equipment. Using a clean system (free ofpotential contaminants) with a pitot-type sampler at isokinetic flowconditions minimizes sampling bias at the sample location. The samplelocation within the ballast system also will affect bias. Sampling froma long, straight section of pipe where the flow is fully developed withminimal turbulence is the best case for a sample point.

In one embodiment, an isokinetic flow velocity is achieved by the use ofa pump downstream of a pitot tube assembly. A first flow sensor on thepitot tube assembly senses the ballast water flow velocity in the ship'sballast water pipe near the sampling point. A second flow sensormeasures the flow rate of the sampled fluid at the pitot tube. Thecontrol system may receive these two signals and instruct the pumpcontroller to change speeds in order to maintain an isokinetic samplingcondition. In one embodiment, in combination with the sampling flowcontrol, the pitot tube can be made equal to the isokinetic diameter.

The sensors and controls associated with the system may determine thewater flow velocity in the ballast pipe and adjust the sampling pumpspeed to maintain isokinetic flow conditions at the sample point. Thisallows the pitot sampler assembly to be used in nearly any marine vesselwith equal effectiveness. The sampling system increases and decreasessampling rates as the main ballast water system changes flow rates,allowing the sampling system to maintain isokinetic conditions as flowschange during operations.

The pitot tube assembly allows flow-through sampling and analysisprocesses using a single connection to the ballast system. This is animprovement over current systems, which require either dumping sampledwater into the marine vessel bilges or into a secondary connection whereresulting samples can be pumped.

The pitot tube assembly connects to and inserts through a shipboardisolation valve. This allows the system to be connected to a ballastsystem without interrupting operations. This is an improvement overcurrent practice that requires ballasting to stop and possible drainageof that ballast water piping both prior and after the sampling occurs.

The closed-loop design with a single connection to the ballast systemmeans that there is very low differential pressure across the samplingsystem. This allows the use of a small circulation pump. Thisclosed-loop design also provides a consistent pressure differential,allowing the selection of a single pump for all applications.

DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of thisinvention will become more readily appreciated as the same become betterunderstood by reference to the following detailed description, whentaken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a diagrammatical illustration of a ballast water samplingsystem;

FIG. 2 is a diagrammatical illustration of a pitot tube assembly;

FIG. 3 is a diagrammatical illustration of the pitot tube assembly;

FIG. 4 is a diagrammatical illustration of a portion of the pitot tubeassembly;

FIG. 5 is an exploded diagrammatical illustration of a pitot tubeassembly;

FIG. 6 is an exploded diagrammatical illustration of the pitot wand;

FIG. 7 is a diagrammatical illustration of a portion of the pitot tubeassembly;

FIG. 7A is a diagrammatical cross sectional illustration of a portion ofthe pitot tube assembly;

FIG. 7B is a diagrammatical cross sectional illustration of a portion ofthe pitot tube assembly; and

FIG. 8 is a schematic diagram of the ballast water sampling system.

DETAILED DESCRIPTION

Referring to FIG. 1, a sampling system 100 is illustrated. The system100 may be used to withdraw samples of fluids and, in particular,ballast water from a ship's ballast water system. However, thedescription of the sampling system used in sampling ballast water ismerely to describe representative embodiments and should not beconstrued as limited for use in only sampling ballast water. The systemis able to filter organisms larger than 50 μm in minimum dimension fromthe ballast water and allow removal of the organisms for off-siteprocessing. Additionally, the system is capable of removing a smallsample of raw ballast water from the ship's ballast water pipe foroff-site processing.

The water sampling system is connected to the ship's ballast water pipe104 via the pitot tube assembly 102. The pitot tube assembly 102includes a housing 108 and a pitot wand 110 within the housing. Thepitot wand 110 can be extendable and retractable within the housing 108to reach the interior of the pipe 104.

The ballast water for sampling may be drawn from a ship's ballast waterpipe 104 using the pitot tube assembly 102 that can be inserted into thepipe 104 during periods of ballast water flow through the pipe 104. Thesample water is passed through a filter and returned to the ballastwater pipe 104 by a circulation pump.

As illustrated in FIGS. 2 and 3, the pitot tube assembly 102 can bemounted on an isolation valve 106 extending from and connected to anyship's ballast water-carrying pipe 104. The pitot tube assembly 102 canbe mounted in any orientation, vertical being merely representative. Thevalve 106 can be a fully ported valve so as to allow the pitot wand 110to be lowered therethrough to reach into the pipe 104, as illustrated inFIG. 3 to be able to withdraw a sample from pipe 104. The housing 108can include a longer upper section 130 and a relatively shorter lowersection 132. The sections can be joined by the use of flanges, known inthe art. The pitot tube assembly 102 also includes an upper flange toclose the upper end thereof and a lower flange with an open center isattached at the bottom. The lower flange can be bolted to the ship'sisolation valve 106.

As described further below, the pitot tube assembly 102 can obtain aballast water sample under isokinetic flow conditions. As used herein,isokinetic flow is established under conditions where the velocity ofthe sample ballast water being obtained at the pitot tube is the same orsubstantially the same as the velocity of the ballast water flowing inthe pipe 104 at the sample point (bulk velocity). The pitot tubeassembly 102 is designed to achieve isokinetic sampling flows fromapproximately 0 to 3.5 meters per second (0 to 12 feet per second), forexample. However, other flow velocities are possible.

Referring to FIG. 3, sample water is drawn from the pipe 104 through apitot tube 112 and then up through the wand 110 and out the nozzle 126(best seen in FIG. 2) on the upper end of the housing 108. Once thesample water has been processed, for example, being filtered and asample being removed for testing, the ballast water is returned throughthe return water nozzle 128 (best seen in FIG. 2) on the housing 108.Two small nozzles can be provided at the upper and lower ends of thehousing 102 to allow the system to be vented and drained during setupand removal.

As illustrated in FIG. 4, the pitot tube assembly 102 of FIG. 2 includesan internal pitot wand 110. The bottom end of the pitot wand 110 isprovided with a pitot tube 112, which ends in a 90 degree elbow andserves as the water sample inlet. The bottom of the pitot wand 110 alsoincludes a flow-sensing instrument 114, such as a paddle wheel sensor,for sensing the velocity of ballast water in the pipe 104. The pitottube 112 and flow-sensing instrument 114 are mounted on two elongatedmembers 136, 138, respectively. Conventionally, a pitot tube is used tomeasure the pressure of a stagnant fluid. However, as used herein,“pitot tube” denotes the inlet nozzle 112 for withdrawing sample waterthat is not stagnant.

The pitot wand 110 is lowered into the ballast water pipe 104 throughthe opened fully ported isolation valve 106 using, for example, ajackscrew 116 (or Acme screw). Jackscrews are known to be used inchanging rotary motion into linear up and down motion, such as would beused to raise and lower the pitot wand 110. However, it is to beappreciated that the pitot tube assembly 102 can be mounted in anyconfiguration depending on the location of the isolation valve 106.

Referring to FIGS. 5 and 6, the pitot wand assembly 110 is more fullyillustrated.

The pitot wand 110 is constructed from a first 136 and second 138elongated hollow member. The pitot tube 112 is connected to the lowerend of the hollow member 136, and is for withdrawing sample ballastwater. The hollow member 136 terminates at and is rigidly connected to aconnecting plate 142. The outer periphery of the connecting plate 142 issized to allow vertical movement within the inside diameter of the uppersection 130 of the housing.

The flow-sensing instrument 114 is connected to the lower end of themember 138. The member 138 also terminates at, and is rigidly connectedto, the connecting plate 142. The member 138 can be for routingelectrical conduit, such as for powering and receiving signals from theflow sensor 114 connected at the bottom end of the member 138.

The pitot wand 110 includes a lower flange 144 that can be rigidlyattached at the lower sections of members 136 and 138. Referring to FIG.6, the lower flange 144 construction is more clearly seen. The flange144 includes an upper section 146 and lower section 148. The uppersection 146 includes an upward projecting holder 150 for receiving theflow measuring instrument 114. The upper section 146 is then insertedvia the projecting holder 150 in the lower end of the hollow member 138.The lower section 148 of the flange 144 includes a downward projectinghollow tube 152 to house the flow measuring instrument 114, such that apaddlewheel-type flow sensor, for example, can project below the end ofthe hollow tube 152. The lower section 148 can be assembled rigidly tothe upper section 146. The lower flange 144 has an outer diameter thatis sized to fit within the inner diameter of the housing 108 so as toalign the pitot wand 110 as it is raised and lowered within the housing108.

Referring to FIG. 5, the elongated members 136, 138 are held together bythe upper connecting plate 142 and the lower flange 144 to move in thehousings 130, 132, as a unit. The connecting plate 142 also includes anut 140 that receives the Acme screw 116. As can be appreciated, turningthe Acme screw 116 will raise and lower the two members 136 and 138simultaneously within the housings 130, 132.

The newly collected sample water and return sample water are separated.The water sample is drawn through the pitot tube 112 and exits from thetop of the member 136. The water sample then exits from the housing 130through the water outlet 126. After processing the water sample, thewater sample is returned via the water return inlet 128 in the lowerhousing 132. The newly drawn water sample is separated from the returnwater sample via the use of a plate 160 positioned at the top of thelower housing 132. The plate 160 includes seals 162 and 164 (best seenin FIGS. 7A, 7B) that surround the members 136, 138, respectively, toprevent the contamination of the newly drawn water sample with thereturn water sample. The seals 162, 164 also allow the members 136, 138to slide therein when being raised and lowered.

Because the upper end of the hollow member 136 is hollow, it can beappreciated that the water sample taken up by the pitot tube 112 willexit the member 136 above the seal plate 160 and then enter the uppersection 130 of the housing and be withdrawn through the water outletnozzle 126. The return water sample will enter via the inlet nozzle 128in the lower section 132 of the housing below the seal plate 160, passthrough the lower flange 144 via a hole 154, and exit into the ship'spipe 104.

The pitot wand 110 includes an inlet nozzle 112 (the pitot tube), whichis set generally at a right angle to the longitudinal axis of the pitotwand 110 and is pointed with the open end in the direction of flow ofthe ballast water through the ballast water pipe 104. It is to beappreciated that the pitot wand 110 is generally inserted in a directionthat is perpendicular to the ballast water pipe 104. In the illustratedcase, the pitot wand 110 is set vertically because the illustratedballast water pipe 104 is set horizontally. Therefore, in theillustrated embodiment, the inlet nozzle 112 is set horizontally andaligned with the ballast water pipe 104. It is to be appreciated that ifthe ballast water pipe 104 is set vertically, then the pitot tubeassembly 102 may result in being horizontal. The ballast water sampleinlet 112 is generally parallel to the direction of flow of the ballastmain pipe 104. The opening in the inlet nozzle 112 leads to the passage136 within the interior of the pitot wand 110.

Referring to FIG. 5, the pitot wand 110 is positioned in the housingsections 130, 132 such that the connecting plate 142 and the open upperend of the member 136 are above the seal plate 160. When withdrawingsample ballast water, the pitot wand 110 is lowered and the shaft seals162, 264 remain in place on the seal plate 160 at the upper end of thehousing 132, such that the open end of the member 136 remains above theseal plate 160 and the sample water return inlet 128. The lower flange144 remains below the seal plate 160 and the sample water return inlet128. The ballast water sample is returned to the ballast water pipe 104via the sample water return inlet 128 on the lower section 132 of thehousing. The return sample water exits the housing 108 around the pitotwand 110 at the lower end thereof, which then leads into the ballastwater pipe 104. The return sample water is released behind the pitottube 112, and behind the flow measuring instrument 114.

In one embodiment, the pitot wand and assembly can minimize bias ofentrained solids (such as organisms) in the sample fluid relative to thebulk fluid.

In one embodiment, the pitot tube assembly 102 can withdraw a 3 cubicmeter sample in 90 minutes, with a ballast water fluid velocity ofapproximately 1.8 meters per second. This requires an open area at thepitot tube 112 mouth of approximately 0.5 square inches for isokineticflow.

In one embodiment, smooth flow around the pitot tube 112 is ensured, andthe mouth of the pitot tube 112 is smooth in profile, including roundand oval shapes at the proximal (front) side of the wand 110, and arounded shape at the distal (back) side.

In one embodiment, the mouth of the pitot tube 112 is greater than 1diameter upstream of any downstream interference in the ballast waterpipe 104.

In one embodiment, the maximum velocity to maintain isokinetic flow isapproximately 3.6 meters per second.

In one embodiment, the flow speed of the sampled fluid downstream of thepitot tube can change from the isokinetic velocity, but can remainsmooth with minimal turbulence-causing geometry.

In one embodiment, a flow sensor 114 is used to measure the speed of theflow in the ballast main pipe 104 to ensure that the flow velocity atthe pitot tube 112 is near or approximately isokinetic. The flow sensorshould be in the free stream and can be removable for maintenance. Inone embodiment, the flow sensor 114 uses a paddle wheel-type flow sensoron the bottom of the pitot wand 110. However, other flow sensor typesmay be used. For example, in one embodiment, ultrasonic sensors can beused on the exterior of the ballast water pipe 104.

As used herein, isokinetic sampling occurs when the velocity of thefluid and the bulk flow in the ballast water pipe 104 matches thevelocity of the fluid at the inlet of the sample tube 112. Isokineticsampling is useful when sampling a fluid that contains entrained solidsor fluids with a density different than the carrier fluid in order toobtain a representative sample. In the disclosed system and method, thediameter of the pitot tube 112 is made a fixed size and can be used inmany different flow speeds because of the ability to reach isokineticflow velocity via the use of sensing ballast water flow velocity in pipe104 and sample flow velocity, and then calculating a difference in flowvelocities and operating a sample water pump so that the sample waterflow velocity in the pitot 112 matches the ballast water flow velocityin pipe 104.

The isokinetic diameter for a sampling pitot tube can be calculatedbased on the fluid flow rate through the main ballast pipe, the fluidflow rate through the sampling apparatus, and the diameter of theballast main pipe. The isokinetic diameter is a well-known number forsizing sample ports as disclosed in Computational Fluid DynamicsAnalysis of Ballast Water Sampling, by E. Lemieux et al.

A feature of the pitot tube assembly disclosed herein is the ability tobe universally used in various ballast water systems regardless of flowof the ballast water, meaning that the system can be installed withequal effectiveness on vessels of different sizes. Different vesselshave different ballast water flow rates, volumes, pipe sizes, etc. Inorder to use the same equipment with equal effectiveness on any vessel,a sampling pump is used to modify the flow velocity enough through thepitot wand to achieve desirable sampling conditions. Thus, the samplepitot tube 112 diameter is not increased larger than the isokineticdiameter, which is the current common method.

In one embodiment, the use of the pitot tube assembly 102 is as follows.

Assuming that the ship ballast water system includes an isolation valveas described, the valve is initially closed, and vessel personnel unboltthe blank flange covering the sample port in the ballast water pipe 104.Then, the pitot tube assembly 102 is bolted onto the shipboard flangeupstream from the closed valve. Hoses may be connected from the samplingsystem to the pitot tube assembly 102. The isolating valve 106 isopened. The pitot wand 110 is lowered into the ballast water pipe 104 byoperation of the jackscrew system 116.

The valves in the sampling rig are aligned, and sampling can begin. Oncethe sampling testing is complete, the pitot wand 110 is retracted by thejackscrew 116, and the isolating valve 106 is closed. Thereafter, thepitot tube assembly can be drained and removed from the valve 106 andthe blank flange reinstalled on top of the valve 106.

In one embodiment, the sampling system may include a controller (PLC 226of FIG. 8) and data recorder with an HMI interface. The purpose is toprovide one controller that can manage and record data from all othersubsystems. The controls and equipment may be contained in a rugged,portable case with interface ports that may allow for connecting to thesub-assemblies for pump control, data acquisition, etc.

In one embodiment, a programmable logic controller (PLC 226) may be usedto collect the input from all sensors and control the sampling pumps.

The PLC 226 may control the operation and speed of the pump motors, aswell as provide the link to the HMI for data display and data logging.The PLC 226 may be a modular type to allow any necessary customizationand to allow for implementation of future technologies.

In one embodiment, the majority of interface to the control system mayoccur through a touch screen interface. Touch screen interfaces arecommercially available displays that may have integrated data loggingcapabilities. Integrating HMI and data logging is useful, since theamount of programming to interface to the PLC is reduced considerably.

Referring to FIG. 8, a schematic diagram is shown illustrating oneembodiment of a sampling system. It is to be appreciated that any pipingmay include shut-off valves to isolate any instrument and/or drain anysection of piping, as well as include the use of temporary piping, suchas hoses, connected via quick disconnects.

The system includes the pitot tube assembly 102, which is connected tothe ship's ballast water pipe 104. As discussed above, a pitot tube islowered in the pipe 104 to withdraw sample ballast water at isokineticconditions. A flow meter is also placed in the pipe 104 to measure theflow velocity of the ship's ballast water flow. The sample ballast wateris transferred via line 214. Line 214 is sensed for flow rate (thesample ballast water flow rate), such as via a magnetic flow meter 212.The velocity at the pitot tube 112 can be calculated, for example fromflow rate and pipe diameters. The pressure in line 214 may be sensedwith the pressure transmitter 200.

The line 214 branches into three branch lines 216, 218, and 220. Branchline 216 leads to a variable speed peristaltic pump 202. Pump 202 is fortaking a portion of the sample ballast water to be used for testing.Branch line 216 then connects to the inlet sample return line 222, whichallows return of the sample ballast water to the ballast water pipe 104.Branch line 220 includes a filter 204 and a differential pressuretransmitter 206 for monitoring the pressure drop in the filter 204. Aflow meter, such as a magnetic flow meter 208, can be provided on line220. The flow through the filter 204 is controlled by the variable speedcentrifugal pump 210. Branch line 218 is for receiving the excess flowto maintain isokinetic flow if the filter 204 is disconnected. A flowcontrol valve 230 controls the flow rate through the filter 204. If thefilter 204 is not present, all the water passes through the bypass line218. Branch lines 218 and 220 combine into combined line 224, whichleads to the variable speed centrifugal pump 210.

The pump 210 controls the water flow from the pitot tube assembly 102through the filter 204 and bypass loop 218. The PLC controller 226 maychange the speed of the pump 210 to maintain an isokinetic samplingcondition at the pitot tube 112. The flow velocity of the ship's ballastwater pipe 104 is determined by the flow sensor 114, which can be at thelower end of the pitot wand 110. The flow velocity through the pitottube may be determined by the flow sensor 212 on the sample water pipe214. Both flow signals may be transmitted to the PLC controller 226, andthe difference in flow velocities can be compared, and, when adifference is sensed, the flow velocity at the pitot tube can beadjusted by the pump 210. Pump 210 can maintain the flow velocity of thesample ballast water through the pitot tube as close as possible to theship's ballast water flow velocity in pipe 104. While one embodiment ofa control system is described, it is to be appreciated that otherconfigurations are possible. For example, a constant flow can bemaintained by the pump 210, while a bypass loop with a control valvefrom the pump discharge to the pump suction controls the amount of flowvelocity at the pitot tube.

The circulation pump 210 can be located downstream of the filter 204 andall suctions to subsystems. This means that there is no risk of organismdeath before being drawn through the filter or into another of thesubsystems.

In order to maintain an isokinetic sampling condition at the pitotassembly, most of the sampled water may pass through the filter or abypass line. If the filter is not in use but other components areoperational, the bypass line may be used or an isokinetic condition maynot exist at the sample point.

In one embodiment, the circulation pump 210 may pull fluid from theballast water pipe 104 through the filter 204. A flow meter 208 maymeasure the flow rate through the filter 204, and the controller PLC 226may integrate this value to determine the volume of filtered fluid. Thismeasurement can be compared to flow measurements taken from the ballastmain pipe 104 to determine the relative scale of the sample fluid to thebulk fluid flow. A ratio of flows can be controlled by the pump 210. Inone embodiment, the filter 204 can be a bag-type filter.

The peristaltic pump 202 allows the sample ballast water to pass throughthe pump without coming into contact with the pump gear, seals, ormoving parts. Since the ballast water is gently moving through the pump,the risk of organism mortality is low. The sample is collected in theportable container 228, for example, downstream from the peristalticpump 202. In one embodiment, the peristaltic pump 202 can rotatequickly, thus pulling a full sample, such as several liters, over ashort duration of time. In another embodiment, the peristaltic pump mayrotate continuously and slowly, giving a continuous sample over a longperiod of the ballast water discharging event. In a third embodiment,the peristaltic pump 202 can rotate intermittently, giving discretesamples over the discharge event. These samples could be combined ortreated separately. The samples can be put into suitable storagecontainers, such as 228, for transportation to off-site facilities foranalysis.

The sample pitot tube is designed to operate at isokinetic conditions.Most of the current ballast water testing guidance recommends a diameterthat is larger than the isokinetic diameter. As discussed previously,this is not desirable in the present embodiment due to spaceconstraints, for example. As disclosed herein, the system uses a pump210 to be able to modify flow velocities to match the different ballastflow velocities on different vessels, while using the same commonsampling pitot tube. This allows a smaller pitot tube to be used with avariety of different vessels.

While illustrative embodiments have been illustrated and described, itwill be appreciated that various changes can be made therein withoutdeparting from the spirit and scope of the invention.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A method for taking asample of ballast water, comprising: withdrawing a sample of ballastwater via a tube inserted in a ballast water pipe, wherein the tubeincludes a sample inlet, and isokinetic sampling is achieved via a pumpthat controls the flow rate of the sample ballast water through the tubeinlet by comparing a fluid velocity of the ballast water pipe with afluid velocity of the sample ballast water through the tube; controllingthe flow of water through the sample tube inlet when a flow velocity ofthe ballast water pipe is sensed to be different than a velocity of theballast water in the pipe; withdrawing a portion of the sample ballastwater for testing; and returning remaining sample ballast water to theballast water pipe.
 2. The method of claim 1, wherein the sample ballastwater is withdrawn and returned via a pitot tube assembly comprising ahousing and a wand inside the housing, wherein sample ballast water iswithdrawn through the wand, and sample ballast water is returned via thehousing.
 3. The method of claim 2, further comprising extending the wandfrom within the housing to reach a sampling location inside the ballastwater pipe.
 4. The method of claim 2, wherein the wand seals against thehousing, and sample ballast water is withdrawn from a location above theseal, and sample ballast water is returned below the seal.
 5. The methodof claim 2, wherein the pitot tube assembly is attached to the ballastwater pipe via an isolation valve.
 6. The method of claim 1, wherein asecond pump is operated to withdraw a portion of the ballast watersample for testing.